FLORISTCS OF RIVERINE VEGETATION IN KALA OVA BASIN

Abstract

Riparian or riverine zones consist of important vegetation that helps tostabilize the stream banks, trap silt and enhance the quality of stream water.However during the last century riverine vegetation has been heavilydegraded due to human impact.

The study in the Kala Oya basin covered Kala Oya and fifteen of itstributaries. The NCR GRADSECT sampling methodology was adopted and5m width 100m or more length 67 plots were randomly set out consideringthe length of the streams. All the trees, > lOcm dbh, saplings> 1m height and< lOcm dbh, seedlings, lm height were recorded.

The results reveal 81 species of seedlings, 81 species of saplings and 61species of trees in the study site. The recorded endemicity of seedling:sapling: tree is 4:2:2. Among the 1080 individuals recorded 532 were >20cmdbh, 539 were > 10m in height and 431 had> 3m canopy cover. The mostrecorded tree species were Terminalia arjuna (270), Pongamia pinnata(161), and Ficus racemosa (91).

The stream wise species to individual ratio vary from 0.128 to 0.600. Fivestreams recorded over 20 species and they are Kala Oya (30), SiyabalanduwaOya (27), Dambulu Oya (25), Welamitiyawa Oya (24) and Kalankuttiya Oya(23).

The most interesting finding is that there is natural regeneration within thezone and only basic silvisultural treatment is required to enhance the process.However in sites where heavy human impacts were observed planting ofsuitable species have been recommended.